1. Field
The present disclosure relates generally to an energy absorbing apparatus and, in particular, to a method and apparatus for securing parts to each other. Still more particularly, the present disclosure relates to a method and apparatus for ensuring bolted joints can withstand destructive force levels using a crushable spacer.
2. Background
When manufacturing objects such as engines or generators that could be used in automobiles or aircrafts, spacers may be used when securing parts to each other using fasteners or bolts. For example, when securing an inlet to an engine case, fasteners in the form of bolts and nuts may be used to attach an inlet to the engine case. In designing an engine, the inlet, engine case, and bolts are selected in a manner that may reduce a risk that the inlet may become detached from the engine case if a blade in the engine becomes detached and/or fails during operation of the engine. The inlet should remain intact and attached to the engine case, and the blades should remain contained within the engine case.
Currently, this type of result is achieved through a selection of the number of bolts and the type of bolts in a manner that provides a capability to withstand forces of high magnitudes that may be applied to the inlet if a rapidly rotating fan blade becomes detached from the engine. The selection of bolts and the design of the inlet and engine case to withstand such forces of high magnitude can increase the weight of the aircraft.
This design may result in an increase in the number of bolts and/or the size of the bolts. The design also may increase the thickness and/or size of flanges for the inlet and engine case where the bolts may be used to secure the inlet to the engine case.
It would be desirable to reduce the weight and/or cost of securing an inlet to an engine case. One currently used solution may involve using a load-absorbing element, such as a crushable spacer. A crushable spacer may be used with a bolt and nut assembly to provide a capability to absorb energy that may be applied to the bolt and nut assembly.
Many existing spacer designs, however, are, in general, inefficient in absorbing energy and may not be as effective in minimizing the transmitted force. As a result, although the spacers may absorb energy, the reduction in weight in the design of the inlet and engine case attachment may not be as great as desired.
Therefore, it would be advantageous to have a method and apparatus that overcomes at least one of the issues described above.